If the pistol doesn't do it for other shooters, it's probably not the pistol. That's good news, because it means there's probbaly nothing wrong with your pistol.
Just because you're "griping" the pistol tightly doesn't necessarily mean you're locking your wrist straight and firmly enough to stabilize the frame during the recoil cycle. (You'll also see this phenomena when someone switches to a heavier recoil spring, and suddenly their grip and wrist support are no longer sufficient for the different recoil cycle characteristics, and they get smacked between the eyes with hot brass.)
Also, sometimes the shape of the grip frame might be just different enough in some minor way that your grip and wrist/forearm support might require some slight modification from how you manipulate other pistols.
Have someone watch your hand and arm while you're shooting. If your wrist flexes just a little bit during the recoil cycle ... or is "broken" (bent) in relation to the alignment of your hand and forearm ... even though your fist may be clenched almost painfully tight around the grip frame, you might unintentionally be allowing sufficient movement of the frame during extraction/ejection to have the empty case thrown back at your face.
If this is the case with your "problem", straightening and locking your wrist may resolve it. I'd try that before I'd have someone "modify" any part of the pistol, especially the ejector/extractor. Sometimes such modifications can create more problems than they "solve", and could actually degrade reliability in other ways. Your pistol is a quality, well engineered weapon, and SIG has been making them long enough to have pretty much determined the proper design for the components.
There are variations to this, though, and it's not easy to diagnose without having someone present to watch what's happening while you're shooting.
Oh yeah, it wouldn't hurt to have someone examine the pistol for a quick armorer's check, just to make sure there aren't any burrs on the extractor, no debris in the extractor cut, etc. ... But if it truly is only happening when you shoot it, and it functions fine for everyone else, it's probably something you can fix by modifying your manipulation during shooting.
Best of luck, and don't let it bug you too badly. You don't really think you're the ONLY person to occasionally experience this, do you? The few times a year I take my P-90 to the range and fire it with the 16 pound recoil spring in it (stock is 11 pounds, but for this thread it doesn't matter why I switched), if I allow my grip OR wrist to soften just a litle bit ... I get an empty sailing by my face or bouncing off the top of my head. Proper grip & locked wrist, and all the empties land in a pile out at 4-5 o'clock a few feet away.
